Whatever the fate of Beagle 2, we should acclaim the scientists and technologists who developed it. The challenge was daunting. Only a third of previous attempts to 'soft land' on Mars have succeeded - the US, Russia and Japan have all had failures, despite larger and more expensive spacecraft. The concept behind Beagle 2 was astonishingly bold: to carry out a robot excavation of the surface of Mars, analyse its soil, and beam back the results from a location hundreds of times further away than the Moon.

It was one of the smallest and cheapest of European space missions, but Beagle 2 captivated the public. It aimed to illuminate a question that fascinates everyone: how did life begin? Was its emergence an event unique to Earth, or did it happen elsewhere? Colin Pillinger's high-profile leadership, and the enthusiasm of the scientists and high-tech companies involved, render Beagle a trailblazer for future projects.

To most people in the UK, indeed throughout Western Europe, space exploration is primarily perceived as 'what NASA does'. This perception is - in many respects - a valid one. Superpower rivalry during the Cold War ramped up US and Soviet space efforts to a scale that Western Europe had no motive to match.

In most other technical and economic spheres, Europe can aspire to parity with the United States, if it co-ordinates its effort properly. But the European Space Agency (ESA), though cost-effective and successful, cannot match the scale and range of NASA's activities. Per head of population, we spend only a fraction of what is committed to space research in America.

Most of NASA's budget, however, is committed to manned spaceflight - something that Europe has so far eschewed. Indeed, shoring up the obsolescent Shuttle is proving ever more of a drain on NASA's resources: they are grounded, for at least another year, because of safety concerns. In the meantime, the Space Station, dependent on the Shuttle, seems even more a turkey in the sky - neither practical nor inspiring, with projected total costs now escalating towards $100bn.

By maintaining a focus on unmanned programmes - a policy which the UK has always endorsed - Europe has become fully competitive with the US in scientific spacecraft, as well as having an effective commercial programme. Within Europe it's the French who have been the most vocal enthusiasts for space. They have invested more heavily in ESA; they have developed the Ariane launcher; and Europe's first woman astronaut, Claudie Haignere, is France's Minister for Science.

Mars Express (of which Beagle 2 was the highest-profile component) is just one of ESA's innovative projects. Next year, the Huygens probe will parachute into an even stranger world than Mars - Saturn's giant moon, Titan. And the Rosetta probe will be launched, on a mission to 'soft land' on a comet. ESA's 'XMM Newton' gives us x-ray images of exploding galaxies and cosmic clouds billions of light years away. In 2007 the Planck Spacecraft will map with extraordinary precision the faint microwaves which are the afterglow of the Big Bang - offering clues to what happened in the first trillionth of a trillionth of a second after the 'genesis event'.

All space projects push the frontiers of technology and are drivers of innovation. But ESA's goal is science and exploration - to find out what's out there in the cosmos, to understand it (if we can) and to learn about the basic laws of nature. When the history of modern science can be seen in perspective, this endeavour will provide one of its greatest chapters.

Darwin and his successors taught us how our biosphere evolved, and thereby transformed our conception of humanity's place in nature. In the twenty-first century, space scientists are setting Darwin in a grander cosmic context - probing the origins of Earth, stars, atoms and the universe itself.

We're starting to explore our solar system - each planet is a distinctive world. Just within the past few years, retinues of planets are being detected in orbit about many other stars.

In future, children won't perceive the stars as mere twinkling points of light: they'll learn that each is a 'Sun', orbited by planets fully as interesting as those in our Solar system.

Robotics and miniaturisation are advancing. If there is a robotic Beagle III - and I hope there one day will be - it will push the technical frontiers still further, and face fewer risks.

· Sir Martin Rees is the Astronomer Royal and an astrophysicist based at Cambridge University.